Clinical Diagnostic Accuracy in the Management of Primary Stage I Cutaneous Malignant Melanoma in a Plastic Surgery Unit *

In a retrospective review of 614 primary Stage I cutaneous malignant melanomata and 40 nonmelanoma lesions, the diagnostic accuracy(DA) for malignant melanoma was 86.2%. A positive preoperative clinical diagnosis of malignant melanoma was confirmed histologically in 564/604 (93.3%) of lesions. For 614 histologically proven malignant melanomata a correct pre-operative clinical diagnosis had been made in 564/614 (91.9%). An additional 172 patients were referred for wider excisional surgery within 3 months of a biopsy elsewhere. For the total 786 (614+172) patients, the incidence of biopsy of a clinicially unsuspected (but subsequently histologically proven) malignant mel-


INTRODUCTION
It has been suggested that the clinical diagnosis of cutaneous malignant melanoma poses few problems * Based on a paper read to the Surgical Club of South West England Autumn Meeting 1983, Weston-super-Mare, Friday 21st October 1983.
for the experienced clinician.1 However others2, 3 have emphasised the very variable nature of biopsy techniques currently used on lesions which are later shown histologically to be malignant melanomata, and have highlighted the particular difficulties which inadequate biopsy material creates for the histopathologist in his attempt to correctly microstage the tumour by the methods of Clark4 and Breslow.5 In many series, predominantly from non surgical departments, the reported clinical diagnostic accuracy rate is poor. [6][7][8][9] We therefore sought to define the various pathways to diagnosis for a large number of patients with primary cutaneous malignant melanoma presenting to one surgical unit where malignant melanomata represent 10% of all skin tumours excised annually. The implications of various diagnostic approaches for definitive surgical management of cutaneous malignant melanoma are considered.

MATERIALS AND METHODS
All consecutive admissions for cutaneous malignant melanoma* to the Plastic Surgery Unit at Frenchay Hospital were identified for the 12    Of the 614 histologically proven malignant melanomata a firm pre-operative diagnosis had been made in 564/614 (91.9%) and these had been treated by initial wide margin excision without prior biopsy (Table 2).
During the 12 year period 40 patients were submitted to WE of skin lesions thought clinically to be undoubted malignant melanomata, but which were shown histologically not to be (Tables 3-5). Of the 30 patients treated by wide excision and split thickness skin grafting, only 6 could have been managed by direct wound closure even if MMEB had been employed (either because of the size of the lesion or its anatomical site). If the toe amputation is also   Expressing these data in terms of diagnostic accuracy (DA)9'10, the DA was 86.2%.* When tumours were biopsied prior to referral to the Plastic Surgery Unit, biopsy was most common for lesions of hands/fingers and feet/toes (more than 1 /3rd of lesions), and least common (less than 20%) for lesions of the head and neck or lower limbs (Table 1). DISCUSSION Although the Plastic Surgery Unit at Frenchay Hospital has long served as a referral centre for cutaneous malignant melanoma, it also treats large numbers of patients with other skin neoplasms (benign and malignant). Therefore many patients are referred to the Unit without any previous specialist diagnosis. The level of diagnostic accuracy (86.2%) determined from this study approaches the figure of over 90% which Clark11 has suggested should be achieved, and far exceeds figures for DA determined for previously published series of small numbers of patients with proven malignant melanoma (Table 6). This high level of clinical diagnostic accuracy must be considered against the background of the specific surgical policy in force during the review period. It seems likely that, conscious of the large size of defect they will create, surgeons may be particuarly critical in their clinical assessment of skin lesions which may be potential melanomata. reported an 84% accuracy of positive pre-operative diagnosis when all lesions were examined clinically with skin microscopy.14 The comparable figure for naked eye assessment (by some 14 surgeons) in the present series is 93.3%.
In the present series of all cases of histologically proven cutaneous Stage I malignant melanoma treated primarily by the Plastic Surgery Unit 91.9% were managed by initial wide excision on the basis of clinical appearance alone, without prior biopsy of any sort. A further 40 lesions were similarly excised widely but proved not to be melanoma (Tables 4 and  5). These 40 patients represent 6 16 (19.5%) proved to be for non melanoma lesions. Rather than being employed routinely, frozen section is likely to be most valuable in distinguishing melanocytic from non-melanocytic lesions when doubt exists clinically,16 but it may prove very difficult with this technique to differentiate benign from malignant naevocytic lesions at the dermo-epidermal junction.17 Frozen section techniques will also pose diagnostic problems in lesions exhibiting regression, and frozen section specimens are likely to be thicker than comparable paraffin section specimens.18 Therefore when reports of maximal tumour thickness are given, it should be made clear whether these measurements have been made on frozen or paraffin section preparations. This has become particularly important since the adoption of routine measurement of maximal tumour thickness in the histological assessment of primary malignant melanoma.5 Although we do not know how various biopsy techniques (incisional, shave, punch etc) affect prognosis in malignant melanoma,19,20 the most compelling reason for avoiding inadequate biopsy methods is the tissue distortion that these may cause.
The histopathologist can only accurately microstage the tumour (at present most importantly by measuring the maximal thickness) if he is presented with the whole lesion surrounded by an adequate 'cuff of adjacent normal tissue to which the tumour may be related. Even such narrow margin excision biopsy may sometimes create a defect which cannot be sutured directly and may require skin grafting. This is likely to be particularly true for lesions of feet/toes and hands/fingers where there is minimal tissue laxity; in the present series 20/55 (over 1 /3rd) of lesions in these sites were biopsied prior to referral for definitive surgery. A higher index of suspicion for the diagnosis of malignant melanoma in these peripheral sites is clearly needed. Compromise of the adequacy of such tumour excision biopsy in these areas could be avoided by referral to a surgical unit.
Although this study relates to data for a period when wide margin excision of all suspected melanoma lesions was the policy, it should be emphasised that this report should not be construed as advocating such wide margin excision as definitive treatment for cutaneous malignant melanoma now.
The optimal resection margins (to limit the incidence of local tumour recurrence) have yet to be determined, and recently several groups of workers have questioned conventional excision margins and have variously suggested reduction in clearance margins.21 ~23 With the rising incidence of cutaneous malignant melanoma in this country,24 all clinicians should familiarise themselves with the irregularities of colour, surface contour and margin which are the hallmarks of the tumour. 25 High levels of diagnostic accuracy in the management of malignant melanoma of the skin need not be restricted to Plastic Surgery Units, but clearly referral centres dealing with large numbers of cases have the advantage of experience.